1. Field of the Invention
This invention relates to steel studs, trusses and joists comprising parallel flanges extending orthogonally from web sides, and more particularly to a stud, truss or joist with at least one slot in the web and including supplemental flanges extending from slot sides within the web. The steel studs, trusses and joists also comprise primary flange material folded back into the channel and running parallel along the primary flange. This material also extends along the root of the ninety degree radius connecting the primary flanges and the web sides.
2. Prior Art
Interior wall construction using horizontal channel beams as headers and footers and matching vertical studs received into the channel beams is well-known. Commonly, the studs are also channel-shaped and both are made of metal, typically cold formed metal and, typically steel. Similarly, metal buildings employ girts (sidewall bracing) and perlins (roof bracing). Roof rafters, headers, footers, beams and joists can also employ channel shaped members. (For purposes herein, use of the term “stud,” “metal stud,” “steel stud” and “building stud” are not meant to be restrictive or limitations but are meant generically to be synonymous and to include all materials from which such studs may be formed.)
Of all modes of failure, buckling (Euler or local) is probably the most common and most catastrophic. That is, a structure may fail to support a load when a member in compression buckles, that is, moves laterally and shortens in length. A steel stud may be described for these purposes as a slender column where its length is much greater than its cross-section. Euler's equations show that there is a critical load for buckling of a slender column. With a large load exceeding the critical load, the least disturbance causes the column to bend sideways, as shown in the inserted diagram, which increases its bending moment. Because the bending moment increases with distance from a vertical axis, the slight bend quickly increases to an indefinitely large transverse displacement within the column; that is, it would buckle. This means that any buckling encourages further buckling and such failure becomes catastrophic.
The traditional steel stud construction comprises a pair of parallel flanges extending orthogonally from a web. Commonly the flange distal end bends inward slightly to increase the compressive stability converting the flat two-dimensional flange into a three dimensional structure. For these purposes, “compressive stability, strength or stress” means a reference value that measures the load a structure can sustain before it buckles or otherwise deforms and loses support for a load.
Such studs are very poor energy conservers. For example, for internal walls the metal stud acts as a thermal conduit and actually enhances thermal conductivity across the wall over wood and other materials. In metal buildings the studs (girts and perlins) are in direct metal-to-metal contact with the outside material sheeting and become conduits of heat on the outside sheeting to inside the building. Heat passes through the web, so one interested in reducing thermal conductivity might consider removing material from the web to create slots in the web. To the extent such slots remove metal and thus reduce the thermal path, the stud is less conductive thermally. Also, such slots may receive insulation that further impede conductivity.
Similarly, a steel stud is a good acoustic conductor, which is detrimental in many applications. It has long been desired to reduce sound transmission through metal wall studs. As in thermal conductivity, re-shaping of a significant portion of the web or the flanges will reduce the acoustic conductivity of the stud and therefore the wall.
It is a primary object of the present invention to enhance the compressive stability, strength and bending resistance of a traditional steel stud. It is another object to reduce thermal conductivity and acoustical transmission, of the stud while enhancing the bending resistance and compressive stability and strength. To this end, it is a further object to introduce one or more slots in the stud web that interrupt conductivity across the web in combination with projections from the web at the slots additional to the primary flanges that enhance the load that a stud can support under bending and compression. It is a further object to provide indentations in the stud to enhance the strength of the stud and overcome weaknesses that are introduced at slot corners between slot ends and slot vertical sides.